Brown the meatballs in batches, turning them to brown on all sides. Remove the browned meatballs from the pressure cooker and set them aside.
Make the sauce. Add the onions and red pepper to the cooker and sauté until they start to soften – about 3 minutes. Stir in the garlic, Italian seasoning, sugar (if using), 1 teaspoon of salt, black pepper and crushed red pepper flakes. Add the crushed tomatoes and the petite diced tomatoes and cook for a few more minutes. Then return the meatballs to the pressure cooker and stir to coat them in the sauce.
Break the dried pasta in half and spread it out flat on top of the meatballs in different directions. Sprinkle ½ teaspoon of salt over the pasta. Pour the water and chicken stock on top of the pasta and press the pasta down gently to submerge it into the liquid. No need to stir, but make sure the liquid in the cooker is able to reach the bottom of the cooker by pulling the ingredients away from the side of the cooker a couple of times before locking the lid in place. If the cooker gives you an error message, open the lid and stir the ingredients just a little, making sure the water can reach the bottom of the pot.
Pressure-cook on HIGH for 6 minutes.
Make the whipped ricotta. Whisk the ricotta cheese, Parmesan cheese, milk, parsley and basil together in a bowl. Season with freshly ground black pepper.
Release the pressure using the QUICK-RELEASE method, covering the pressure release valve with a kitchen towel if it starts to spurt a little water.
NOTE: For a short cut you can use two (24-ounce) jars of your favorite pasta sauce instead of making the sauce yourself, increasing the water to 2½ cups. Pour the sauce over the browned meatballs and continue with step 5.
NOTE: If you are using a brand of petite diced tomatoes that are thick, like Cento®, you may need to add another ¼ cup of water to the pot before pressure cooking.